Transport: Powerful Secret

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Alongside the Indianapolis motor speedway is the most secretive aircraft engine plant in the U. S., the Allison Engineering Co. factory, wholly owned by General Motors. There the sleek 1,200-h.p. motors that power the Army's fastest ships are built. Because the Air Corps takes the entire output of the plant, uses them to power speedy Lockheed, Bell and Curtiss pursuit ships and Bell cannon-carrying fighters (see p. 15), every Allison is a Prestone-cooled secret.

Last week, however, Allison had its newest secret, the world's most powerful aircraft engine, on display in G. M.'s Building on New York's World's Fair grounds for all to see. Because it was displayed as casually as Poe's purloined letter, few visitors paid any attention to it.

The new engine has 24 cylinders ar ranged in four banks like a double-V. Supercharged and built for streamlining into wings and fuselages, it develops 2,400 h.p., weighs less than a pound per horse power.† Its constant-speed propeller, largest ever built in the U. S., is geared to revolve at lower speed than the engine (because propellers lose efficiency at high speeds). Probable use of the new powerplant: to propel bombers faster than bombers have ever been driven before.